1. Field of the Invention
The present invention relates to an organic thin film transistor, a flat display device including the same, and a method of manufacturing the organic thin film transistor. More particularly, the invention relates to an organic thin film transistor that easily obtains a patterning effect of an organic semiconductor layer and improves characteristics such as an on/off ratio, a flat display device including the organic thin film transistor, and a method of manufacturing the organic thin film transistor.
2. Description of the Related Technology
Flat display devices such as liquid crystal display devices (LCDs) or electroluminescence display devices (ELDs) use a thin film transistor to serve as a switching device for controlling an operation of a pixel and a pixel-driving device.
The thin film transistor includes a source electrode and a drain electrode facing each other, a semiconductor layer including a channel region formed between the source electrode and the drain electrode, and a gate electrode insulated from the source electrode, the drain electrode, and the semiconductor layer.
When the thin film transistor having the above-described structure is formed in an array, since it acts as an independent switching device, the semiconductor layer may be preferably patterned in order to prevent cross talk between adjacent thin film transistors. In conventional silicon thin film transistors, photolithography is used to pattern silicon semiconductor layers.
Meanwhile, as research for flexible flat display devices continues, attempts to use a plastic substrate instead of a glass substrate have been made. However, since the plastic substrate cannot undergo high temperature processing, conventional silicon thin film transistors need to be replaced.
Therefore, methods of forming a thin film transistor on a plastic substrate at a low temperature have been suggested. In particular, research has been conducted into the manufacturing of an organic thin film transistor at a low temperature, i.e., a thin film transistor in which an organic semiconductor layer is formed. However, the organic semiconductor layer cannot be patterned using conventional photolithography. This is because a conventional method combined with a wet or dry type etching process can damage the organic semiconductor layer.
Also, the organic thin film transistor has disadvantages in that since an organic semiconductor material has a very high resistance, its mobility and on/off ratio are low, and if a gate electrode does not provide a sufficient channel to the organic semiconductor material, a current does not flow between a source electrode and a drain electrode.